Carbon transfer in the western South China Sea - biogeochemical perspectives on organic carbon pools in surface sediments, from source to burial
Abstract
Organic carbon (OC) entrainment, transmission and transformation along the terrestrialmarine continuum is fueled by terrestrial sources, modified by progressive in-situ mixing,
production, and decomposition of marine OC.
Bulk (OC, Nitrogen), molecular (Fatty acid methyl esters, FAME) and isotopic (δ
13Corg,
Δ
14C) geochemical data are used in combination with mineral surface area and advanced
computational models (Bayesian statistics, inversion models) to identify OC sources and
their geochemical composition in estuarine and marine surface sediments of the South
China Sea (SCS). A novel inversion modelling approach is presented that estimates OC
pools (incl. petrogenic and dead carbon) validated against end-members. Dominance of
marine OM is confirmed for coastal environments, implying efficient net loss of
terrestrial OM, as it crosses the land-sea interface. The Δ
14C values range from modern
to ~-970‰, with oldest OC focussed to the Red River outflow and remote regions of the
Sunda Shelf palaeoriver systems, modern marine surface sediments are dominant in
oceanic and shelf areas, which contrasts results from other studies from different
river-marine shelf-open ocean systems available in the literature (e.g. the northern part of
the SCS). Also reported, for the first time, anthropogenic synthetic organic compounds
demonstrating the impact of potential pollution on the modern marine environment.